Pyrolytic decomposition of silicon-bearing gas in fluidized beds is an attractive process for producing polysilicon for the photovoltaic and semiconductor industries due to excellent mass and heat transfer, increased surface for deposition, and continuous production. Compared with a Siemens-type reactor, the fluid bed reactor offers considerably higher production rates at a fraction of the energy consumption.
A common problem in fluid bed reactors is fouling of interior components as silicon deposits form on the walls, interior support structures, and interior reactor components including, but not limited to probes, sensors, nozzles, heating/cooling components, feed lines, and sampling lines. Another common problem is contamination of the fluid bed at high operating temperatures by materials used to construct the reactor and its interior components. For example, nickel has been shown to diffuse into a silicon layer from the base metal in some nickel alloys. Silicon-coated particles can be contaminated by the transferred metal. Galling also causes wear and tear of metal components, leading to reactor downtime as components are replaced or the metal surfaces are ground or machined to return them to condition for reuse. Similar problems arise in fluid bed reactors configured for pyrolytic decomposition of a germanium-bearing gas to produce germanium-coated particles. Thus, there is a need to reduce contamination of the product particles formed in a fluid bed reactor and/or reduce wear-and-tear of the reactor components.